Pro-Con Debate: Viscoelastic Hemostatic Assays Should Replace Fixed Ratio Massive Transfusion Protocols in Trauma

Viscoelastic testing: Critical appraisal of new methodologies and current literature

United States Food and Drug Administration (FDA)-approved viscoelastic testing (VET) methodologies have significantly changed in the last 10 years, with the availability of cartridge-based VET. Some of these cartridge-based methodologies use harmonic resonance-based clot detection. While VET has always allowed for the evaluation of real-time clot formation, cartridge-based VET provides increased ease of use as well as greater portability and robustness of results in out-of-laboratory environments. Here we review the use of VET in a variety of clinical contexts, including cardiac surgery, trauma, liver transplant, obstetrics, and hypercoagulable states such as COVID-19. As of now, high quality randomized trial evidence for new generation VET (TEG 6s, HemoSonics Quantra, ROTEM sigma) is limited. Nevertheless, the use of VET-guided transfusion algorithms appears to result in reduced blood usage without worsening of patient outcomes. Future work comparing the new generation VET instruments and continuing to validate clinically important cut-offs will help move the field of point-of-care coagulation monitoring forward and increase the quality of transfusion management in bleeding patients.

Etiology and management of hypofibrinogenemia in trauma

PURPOSE OF REVIEW

Fibrin polymerization is essential for stable clot formation in trauma, and hypofibrinogenemia reduces hemostasis in trauma. This review considers fibrinogen biology, the changes that fibrinogen undergoes after major trauma, and current evidence for lab testing and treatment.

RECENT FINDINGS

Fibrinogen is a polypeptide that is converted to fibrin by the action of thrombin. During trauma, fibrinogen levels are consumed and reduce within the first few hours because of consumption, dilution, and fibrinolysis. Fibrinogen levels usually rebound within 48 hours of injury and can contribute to thrombotic events. The Clauss fibrinogen assay is the gold standard test for fibrinogen levels, although viscoelastic hemostatic assays are often used when a lab delay is anticipated. An evidence-based threshold for fibrinogen replacement is not well established in the literature, but expert opinion recommends maintaining a level above 150 mg/dl.

SUMMARY

Hypofibrinogenemia is an important cause of nonanatomic bleeding in trauma. Despite multiple pathologic causes, the cornerstone of treatment remains fibrinogen replacement with cryoprecipitate or fibrinogen concentrates.

Thromboelastometry-guided haemostatic resuscitation in severely injured patients: a propensity score-matched study

BACKGROUND

To accelerate the diagnosis and treatment of trauma-induced coagulopathy (TIC), viscoelastic haemostatic assays (VHA) are increasingly used worldwide, although their value is still debated, with a recent randomised trial showing no improvement in outcome. The objective of this retrospective study was to compare 2 cohorts of injured patients in which TIC was managed with either a VHA-based algorithm or a conventional coagulation test (CCT)-based algorithm.

METHODS

Data were retrieved from 2 registries and patients were included in the study if they received at least 1 unit of red blood cell in the first 24 h after admission. A propensity score, including sex, age, blunt vs. penetrating, systolic blood pressure, GCS, ISS and head AIS, admission lactate and PT_ratio, tranexamic acid administration, was then constructed. Primary outcome was the proportion of subjects who were alive and free of massive transfusion (MT) at 24 h after injury. We also compared the cost for blood products and coagulation factors.

RESULTS

From 2012 to 2019, 7250 patients were admitted in the 2 trauma centres, and among these 624 were included in the study (CCT group: 380; VHA group: 244). After propensity score matching, 215 patients remained in each study group without any significant difference in demographics, vital signs, injury severity, or laboratory analysis. At 24 h, more patients were alive and free of MT in the VHA group (162 patients, 75%) as compared to the CCT group (112 patients, 52%; p < 0.01) and fewer patients received MT (32 patients, 15% vs. 91 patients, 42%, p < 0.01). However, no significant difference was observed for mortality at 24 h (odds ratio 0.94, 95% CI 0.59-1.51) or survival at day 28 (odds ratio 0.87, 95% CI 0.58-1.29). Overall cost of blood products and coagulation factors was dramatically reduced in the VHA group as compared to the CCT group (median [interquartile range]: 2357 euros [1108-5020] vs. 4092 euros [2510-5916], p < 0.001).

CONCLUSIONS

A VHA-based strategy was associated with an increase of the number of patients alive and free of MT at 24 h together with an important reduction of blood product use and associated costs. However, that did not translate into an improvement in mortality.

Emerging technology for early detection and management of postpartum hemorrhage to prevent morbidity

Despite advances in hemorrhage detection and management, postpartum hemorrhage remains the single leading cause of maternal death worldwide. Within the United States, hemorrhage is the leading cause of maternal death on the day of delivery and within the first week after delivery. Blood transfusion after hemorrhage represents a large proportion of severe maternal morbidity during and after delivery. Blood loss during delivery has historically been assessed visually by inspecting soiled pads, linens, and laparotomy sponges. These methods underestimate the volume of blood loss by as much as 40%, becoming increasingly inaccurate as blood loss increases. Young, healthy obstetrical patients compensate for blood loss via peripheral vasoconstriction, maintaining heart rate and blood pressure in a normal range until over 1 L of blood has been lost. A significant decrease in blood pressure along with marked tachycardia (>120 bpm) may not be seen until 30% to 40% of blood volume has been lost, or 2.0 to 2.6 L in a healthy term pregnant patient, after which the patient may rapidly decompensate. In resource-poor settings especially, the narrow window between the emergence of significant vital sign abnormalities and clinical decompensation may prove catastrophic. Once hemorrhage is detected, decisions regarding blood product transfusion are routinely made on the basis of inaccurate estimates of blood loss, placing patients at risk of underresuscitation (increasing the risk of hemorrhagic shock and end-organ damage) or overresuscitation (increasing the risk of transfusion reaction, fluid overload, and alloimmunization). We will review novel technologies that have emerged to assist both in the early and accurate detection of postpartum hemorrhage and in decisions regarding blood product transfusion.

Advances in the Management of Coagulopathy in Trauma: The Role of Viscoelastic Hemostatic Assays across All Phases of Trauma Care

Uncontrolled bleeding is the leading cause of preventable death following injury. Trauma-induced coagulopathy can manifest as diverse phenotypes ranging from hypocoagulability to hypercoagulability, which can change quickly during the acute phase of trauma care. The major advances in understanding coagulation over the past 25 years have resulted from the cell-based concept, emphasizing the key role of platelets and their interaction with the damaged endothelium. Consequently, conventional plasma-based coagulation testing is not accurate in predicting bleeding and does not provide an assessment of which blood products are indicated. Viscoelastic hemostatic assays (VHA), conducted in whole blood, have emerged as a superior method to guide goal-directed transfusion. The major change in resuscitation has been the shift from unbridled crystalloid loading to judicious balanced blood product administration. Furthermore, the recognition of the rapid changes from hypocoagulability to hypercoagulability has underscored the importance of ongoing surveillance beyond emergent surgery. While the benefits of VHA testing are maximized when used as early as possible, current technology limits use in the pre-hospital setting and the time to results compromises its utility in the emergency department. Thus, most of the reported experience with VHA in trauma is in the operating room and intensive care unit, where there is compelling data to support its value. This overview will address the current and potential role of VHA in the seriously injured patient, throughout the continuum of trauma management.